Currently, variable displacement hydraulic piston units, such as pumps, motors and the like, typically utilize a hydraulic or electro-hydraulic system for changing swash plate angle for varying displacement. It is also known to vary timing by changing the angular position of the port plate of a unit using various means, including a stepper motor and gear arrangement.
However, the typical known hydraulic valves utilized for controlling displacement are generally complex and expensive. It is also desirable to have an alternative to changing port plate position for varying timing. Still further, with the trend toward increased electronic control of hydraulic systems, it is desirable to integrate hydraulic piston unit displacement and timing in an electronic format with other electronically controlled functions.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.